Apparatus for coating wires and the like



April 15, 1941. ,E. J. FLYNN APPARATUS FOR COATING WIRES AND THE LIKE Filed July 14, 1937 Ihventor: Edward J. FIynn,

His Attorney.

Patented Apr. 15, 1941 UNITED STATES PATENT OFFICE 2,238,687 srrsas'rvs roa COATING wmas AND 'rna LIKE Edward J. Flynn, Schenectady, N. Y, assignor to General Electric Company, a corporation of New York 11 Claims.

This invention relates to apparatus for applying liquid coating compositions such as enamels, varnishes, lacquers, etc., to metallic conductors in elongated form. The invention is especially concerned with means for coating wire and the like with viscous liquid coating compositions, including a viscous solution of a resinous composition obtained by condensing an aldehyde, such as formaldehyde, with a hydrolysis product of a polyvinyl ester, such as polyvinyl acetate. Specifically my invention provides a novel die assembly for coating wires and the like with liquid coating material, which assembly comprises a die having unitary apertured means for uniformly reducing to predetermined thickness the coating on the article being coated and mechanical mounting means contacting said die by which the die is movably positioned to provide for free but limited lateral and longitudinal movement of the die during the coating operation.

It is an object of the present invention to provide an improved method and apparatus for coating wire and the like with liquid coating composition, whereby the wire may be uniformly coated, the thickness of the individual coats and thus the total thickness definitely may be controlled, the number of coats required to attain a desired thickness may be lessened, the coating may be applied at a higher rate of wire travel, and solvent losses may be decreased.

Another object of the present invention is to provide means for coating wire and the like with solutions of resinous compositions which, in concentrations that are practical for use in 'enameling wire, are so viscous as to render their application to wire diflicult with such wire-enameling apparatus as heretofore has been available.

The stated objects are attained in accordance with the present invention by passing freshly coated wire or the like through a device which is able to move or float with the wire. Such a device, is, in its practical effect, a self -centering die, that is, a device which centers itself with respect to the wire passing therethrough, irrespective of the movement or the position of the wire.

In the accompanying drawing Fig. 1 is a vertical cross-section of an apparatus for applying liquid coating composition to wires, which apparatus embodies features of my invention; Figs. 2 and 3 are perspective views, and Fig. 4 is a perspective view partly in section, of freely movable, self-centering dies illustrating means employed in accordance with the present invention for providing a wire with a uniform coating of varnish or the like; and Fig. 5 shows graphically the relationship between viscosity and percentage base content of a typical wire enamel.

In the manufacture of electrically insulated metallic wires wherein the insulation is of the so-called "organic enamel" type, the wire usually is passed continuously first through a bath of enamel, varnish or similar liquid coating material, for example an oleo-resinous varnish. On leaving the bath the coated wire is treated, for example, by passing it, usually in a vertical upward direction, through a heated oven to evaporate the solvent and to harden the coating. Appropriate temperature and atmospheric conditions are maintained in the oven so as to produce on the wire a hardened film having the desired characteristics. Heating the coated wire at such elevated temperature as, for example, about 350 C. ordinarily is sufllcient to obtain the desired results. The higher the temperature employed, the shorter is the heating period; and, conversely, the lower the temperature, the longer is the heating time. In practice, it is necessary to coat the wire a number of times, usually from four to eight times, in order to obtain an insulating layer of the desired thickness.

According to conventional practice it is necessary to work with varnishes represented by the more or less horizontal portion of a curve such as shown in Fig. 5. This is due to the fact that in traveling through a bath of very viscous varnish, such as indicated at point A of the curve, at any speed commercially practical, the wire is coated with a layer of wet varnish several times the thickness desirable for efiective drying and for the formation of a smooth, uniform film. For this reason it has been common practice to dilute the base material with solvent, thereby to produce a varnish such as that represented, for example, by the point B on the curve, and to pass the wire a number of times through the thus diluted varnish, baking the coated wire after each passage through the coating bath.

The disadvantages of such a process of coating wires may be summarized as follows: (1) Large solvent losses occur. Such losses often are as much as to per cent of the total liquid applied. (2) Numerous coats are required, if the coating operation is to be carried out at reasonable rate of .wire travel. (3) Difliculty is encountered ln controlling the thickness of the individual coats. and thus the total thickness, due to such influencing variables as, for example, rate of travel of wire through the bath, and surface tension and viscosity of the liquid coating composition. These diiilcuities become so great when working with a high viscosity varnish, such as represented by point A on the curve of Fig. 5,.

of high viscosity and to pass the coated wire through, or otherwise in contact with, wiping devices made of felt or other fabric or fibrous material, for the purpose of removing excess coating material. Wipers made of metal also have been tried. Wiping devices previously proposed or tried have been rigidly attached to a support and have not been freely movable with the wire passing therethrough. Rigid wipers have been objectionable in that, if composed of fabric or fibrous material, the wet coating was rendered uneven, with resultant lack of uniformity in the thickness of the baked coating. In the case of rigidwipers made of metal or other hard substances, the side sway of the wire as it passed through such wiper resulted in removal of the wet coating from the wire in spots, thereby rendering the dried coating non-uniform. It also resulted in excessive wear of the die opening.

The manner in which my invention may be applied-to conventional wire-coating apparatus is schematically illustrated in Fig. 1. As shown in this figure a wire I is drawn from a pay-01f reel 2 over a driving sheave 3 and a guide sheave 4 immersed in liquid coating material 5 contained in a container or vessel 6. Preferably as the wire enters liquid 5 it passes through a wiper 1, formed of felt or other soft, pliable, closely woven or compacted material. The wiper is partly submerged inthe bath of coating material and is wetted throughout its non-immersed portion by capillary action. It is held in place by any suitable means. The numeral 8 designates generally a die and supporting structure used in removing excess coating material from the freslfiy coated wire, specific embodiments thereof being shown by way of illustration in Figs. 2, 3 and 4. The die is in 'operative relationship with the vessel 6. At 8 is shown means for limiting the upward movement of the die with the movement of the wire therethrough. Such means conveniently may take the form, for example, of a member such as a plate rigidly held in place and having an opening sufficient forthe passage of the wire but insufiicient for the passage of the die. The wire with a uniform layer of coating composition of the desired thickness thereon then passes upwardly through a drying or baking oven 9a, consisting of electric heating units III supported within a cylinder II, which is adequately insulated. A port I2 having a damper I3 providm means for controlling the air supply to the oven. Of course it will be understood that any suitable design of baking oven may be employed, and that such oven may be heated with gaseous combustion products, electric heating units or by any other suitable means. The wire with its heat-hardend insulating coating thereon is passed over pulley I4 to a take-up reel (not shown).

The die structure shown in Fig. 2 comprises a member I5 provided with an aperture I6 located equidistant from the opposite marginal edges of said member. The diameter of this aperture is slightly more than that of the wire I which is shown as passing upwardly therethrough.

Member I5 may take a variety of forms, the important consideration being that itmust be free to move with any swaying movement of the wire passing through its central aperture. For example, the member may be spherical, conical, pyramidal, or in the form of a truncated cone or pyramid. Such bodies may be solid, but more suitably may be of hollow form with an open lower or base section. The member I5 also may take the form of a thin, fiat or concave or convex plate, the marginal edges of which are such that the member is round, square, rectangular, hexagonal, octagonal or the like. A preferred form is a thin, fiat plate, such as shown in Fig. 2,

which plate may weigh, for example, about two to three grams. Such a die, as well as others made in accordance with this invention, may be formed from any suitable non-porous material which is unaifected by the liquid coating material. For example, it may be made of, or surfaced with metal or alloys such as tin, copper, aluminum, bronze and the like.

The member I5 rests upon a suitable support adapted to receive it, which support conveniently may take the form of a bracket comprising rods I1 and Ila. This bracket has an opening for passage of the wire I therethrough and is held rigidly in place by any suitable means, preferably at a level slightly above the point of exit of the coated wire from the liquid coating bath 5 (Fig.

1). Should the member I5 tend to move upward with the movement of the wire passing through aperture I6, it may be limited in its travel on the wire'by the use of a rigid member such as the member 9 (Fig. 1) more fully described hereinbefore.

The die structure or assembly shown in Fig. 3 is an integral structure comprising a top section or wall I8, advantageously in the form of a thin, fiat plate .as shown, but which may be of various other shapes such, for instance, as those mentioned when describing member I5 (Fig. 2). The top section I8 is provided with an aperture I9, which is slightly larger in diameter than that of the wire to be received therein and is located equidistant from the opposite marginal edges of said section. Spaced apart from the top section and rigidly united thereto is a bottom section so constructed and arranged as to provide an opening substantially larger than the aperture in the top section, the center of which opening is in alignment with the aforesaid aperture.

The bottom section may take the form illustrated in Fig. 3. As there shown, annularly arranged below the top section or wall I8, parallel therewith and rigidly united thereto, for example as shown in the figure at the points 20, 20a and 20b by means of the rigid connecting members 2|, 2Ia and 2Ib, made of stiff wire, rod, tubing or other substantially non-flexible material, are the cooperating guides 22, 22a and 221), which may be either spheres or discs. For purpose of illustration these guides are shown in Fig. 3 as being spheres. The term "sphere as used hereinafter is intended to include within its meaning a disc, the sides of which are either flat, convex or concave but which preferably are convex. The annularly arranged spheres are in contact with each other, thereby forming a central opening or wire guide-way between the contacting surfaces thereof through which the wire I may be passed, and thence through the aperture I9.

If desired, the bottom section may consist of only one group of annularly arranged spheres or it may consist of groups thereof, as shown by way of illustration in Fig. 3. Thus, annularly arranged below each of the cooperating guides 22, 22a and 22b, and rigidly connected thereto and maintained in the same plane therewith by the rigid, non-flexible members 23, 23a

and 23b may be the cooperating guides 24, 2411-- and 24b, to which latter other cooperating guides similarly may be attached, as desired or as may be'required.

The annular arrangement of cooperating guides may consist of three guides, as shown in the figure, or of more than three, as desired or as may be required.

To provide a die structure of a particular weight required to maintain such device on the exposed The clearance between the die and the die holder suriaceoi', or only partly submerged in the coator support must be greater than the maximum ing material, the cooperating guides 22, 22a, 22b, movement of the wire while running. Ordinarily 2|, 14a and Illa, especially when in the form of such movement is very small. being of the order spheres, advantageously may be hollow and then of a fractional part of an inch. 0! course it will may be brought to the desired weight by sealing be understood that the side walls 21 and 21a may therein lead shot or other suitable weighting mabe positioned at the marginal edges II, 28a, 28 terial. and 28a, if desired, and a structure such, ior er with floating or self-centering dies such as ample, as the member I (Fig. 1) be used to pre-- shown in Figs. 2 and 3, an end of the wire must vent upward movement or the wire. be passed upwardlythrough the die. Fig. 4 is From the foregoing description it will be seen illustrative of a freely movable, self-centering die that the apparatus shown in Fig. 4 includes means which is somewhat more convenient to apply to, slidably supporting the die, specifically apluraland remove from a wire. Further, its arrangeity of transverse rods, for limited lateral and ment permits knobs or enlarged sections of the longitudinal movement of the die, and restrainwire to pass through more readily. ins means, specifically a stop paced from the The die shown in Fig. 4 is an integral strucdie, for limiting its longitudinal movement. ture comprising top and bottom parallel sections Preferably the die assembly shown in Fig. 4,.

or walls It and It spaced apart by the parallel and in all cases at l ast the t p a l th of. is side walls 21 and 21a. The side walls preferably made of resilient metal such, for example, as are positioned inwardly from the marginal edges sheet phosphor bronze. By using such a metal, 28, 28a, 28 and 29a, of the top and bottom walls the sections of the top wall can beforced apart and 26, thereby forming channels for a supto pass the wire from the side through the die porting structure or bracket comprising, for inopenins. the eby void n h in onveniences enstance, the rods ll and "a. These side walls 25 countered when an end of thewiremustbepassed may be formed, if desired, by rolling the sheet ough a die. The sections yielding parate material back upon itself, as shown for example to permi e t ted Po s of the e, r at 3|. The top wall 25 is provided with an apermpl r es (knobs due to brazing) to pass ture 32 located equidistant from opposite marthrough the die opening, after which they reginaledges of said wall. The wall II is split or turn to t r o fllml D B tlon.

divided as shown at 33 into two equal closely The size of the die opening required to a l fitting, yieldably s par bl e ti the dividing a desired thickness of coat to wire oi! a particular line being parallel with marginal edges II and 28a. diameter with a particular varnish is determined The bottom wall 23 is slotted as shown at It in a empirically. Its diameter depends not only upon direction parallel to the marginal edges 29 and 35 the diam t of the r t be v d th in. 2911, the inner part of said slot preferably being but m p e. upon the required thickrounded. The center of the rounded inner part 11655 of nsma i n, the total number of coats to be 35 is in alignment with the aperture 32. In the pplied, the viscosity and other characteristics figure the wire I is shown as passing upwardly of the varnish employed. and other influencing through the center of the inner part II or the variables The d pe n s may or may not be slot 34 and through the aperture 32. slightly tapered, narrowing in the direction of In th use of th di tru t r sh w i Fi 4 the upward movement of the wire, as desired or each of the rods 3! and 30a, comprising a bracket as m e r quired- Dies of the kind hereinbeor di s t, i rigidly s d at; l t t n fore described have been used for prolonged peend, by any suitable means, at a level which pref- 4s ds o t w ut ph asing f th die p nerably is slightly above the point of exit of the 8 and with 110 weal the ng indent-t0 coated wire from the liquid coating bath I (Fig. ailect material y the thickness the 1 11:- 1) Should there be any tendency for the die to In the followillfl table are g ve data llustramove upwardly with the the wire passing theretive of the size of opening of a die ll y d in through, such upward movement willbe stopped practicing the present invention under certain by the inner portions of the lower walls of the P colldltiollsne t data also are channels, formed as described and illustrated, as Elven with respect o e 0 8 0 wire in acthey meet the lower portion; of the rods ll and cordallce with Practice e ofore in use and in mm accordance with the invention herein described.

Table I v m Total and views as? Wire thickm in "of Number new n: 32%! 3 Percent r airedinches 275" 0. base ()by wt m e ywt) I Conventional method .0220 .0012 m is :5 rs 4 Method 11 this invention. Dismeuruahopenin ,o.mineh.- .m .0012 lo 13s 04 as It is an important feature of a construction in As clearly shown by comparing the data given accordance with this embodiment of my invenin the foregoing table it is possible to coat wires tion that the rods II and Ila be or a diameter by me ns of the p sent invention with much substantially smaller thanthewidth or depth of more viscous coating compositions, containing the channels, so that the die will not be held 11111 1 8 So an P e o sly has been D08- rigidly but will be free to move to a substantial sible. A material reduction in solvent "losses is extentat right an les tom wire passing through thus eil'ected. A. lesser number v of individually the aperture .32 and with any swaying movement ppli d t 18 171 Drorlde insulaoi the wire from or out of a true vertical plane. 7 o f a desired kn w n h p eentins vention is practiced, as compared with the number required to obtain a coating of the same thickness with methods heretofore in use. .The wire may be passed through the coating bath and drying oven at higher speeds, thus reducing operating costs. Prescribed tolerances for thickness of coating more readily are maintained. Since the total liquid vaporized is much less, the oven draft can be diminished so that less heat is wasted. The eifect of variables such as surface tension and viscosity of the coating material is minimized.

The present invention also makes possible the practical utilization of wire enamels or varnishes having as' the varnish base resinous compositions which in solution state, even when comprising only a comparatively small proportion of the solution, form such highly viscous solutions sectionally divided top wall, said top wall having an aperture of sumcient size to receive such article to be coated, and a bottom wall joining said side walls, said bottom wall having an opening aligned with the aperture in the said top wall. 1

5. A die having spaced apart side walls extending upwardly and being bent inwardly until they meet to form a top wall divided into two closely fitting, yieldably separable sections, said top wall having an aperture of suflicient size to receive a wire or the like therein, a bottom wall joining said side walls, said bottom wall having an openthat it heretofore has been diflicult, from a practical standpoint, to use them for coating wires.

What I claim. as new and desire to secure b Letters Patent of the United States, is:

1. A die for uniformly reducing to size the thickness of coating on a coated wire, said die being free to move longitudinally and laterally with respect to said wire during the reduction to proper thickness of the coating and comprising a top section provided with an aperture slightly larger in diameter than that of a wire to be received therein, said aperture being located equidistant from the opposite marginal edges of said section, and a bottom section spaced apart from said top section and rigidly united thereto, said bottom section having an opening which is substantially larger than the aperture in said top ing aligned with the aperture in the said top wall, and means integral with the walls of the die for retaining the die on a die support.

6. A die for use in coating wiresor the like with liquid coating material, said die being formed 01' resilient material and having spaced apart side walls extending upwardly and being bent inwardly until they meet to form a top wall divided into two equal, closely fitting, yieldably separable sections, said top wall having an aperture slightly larger in diameter than that of the wire or the like to be received therein,-said aperture being located substantially equi-distant from theopposite marginal edges defining said top wall, a bottom wall joining said side walls, said bottom wall having an opening arranged to permit vertical movement of a wire or the like therethrough and through the aperture in the said top wall, and means integral with the walls or the die for retaining the die on a die support.

section and the center of which opening is inalignment with aforesaid aperture.

2. A freely movable, self-centering die for use in coating wires with liquid coating composition in coating wires with liquid resinous composition,

said die comprising a top wall consisting of a thin flat plate of resilient metal provided with an aperture slightly larger in diameter than that of a wire to be received therein, said aperture being located equidistant from the opposite marginal edges of said plate, said plate being divided into two equal closely fitting sections, a bottom wall spaced apart from said top wall by two side wallswhich are parallel with a line sectionally dividing said top wall, said side walls being positioned a substantial distance inwardly from the parallel marginal edges of said top and bottom walls, said bottom wall being slotted part way in a direction parallel with the lower marginal edges of said side walls, the slot formed thereby being rounded at its inner part with the center thereof aligned with the aperture in said top wall and the longitudinal center of said slot being aligned with the line sectionally dividing said topwall.

4. A die for applying a uniform film of coating material on wires and the like comprising a member having spaced apart side walls extending upwardly and being bent inwardly to form a ing an aperture of suflicient size'to receive a wire or the like therein,.said side walls also extending downwardly and being bent inwardly to form a bottom wall joining said side walls, said bottom wall being slotted part way in a direction parallel with the lower marginal edges of said side walls, the slot formed thereby being rounded at its inner end with the center thereof aligned with the aperture in the said top wall, and suitably spaced apart extensions integral with the walls of the die for retaining the die on a die support.

8. A die assembly for coating wires and the like with liquid coating material, said assembly comprising a die having unitary apertured means for uniformly reducing to predetermined thickness the coating on the article being coated and mechanical mounting means contacting said die by which the die is movably positioned to provide for free but limited lateral and longitudinal movement of the die during the coating operation.

9. A die assembly for use in coating elongated metallic conductors with liquid coating material,

provide limited transverse movement of said die in any direction, and restraining means providing limited longitudinal movement of said die.

11. A die assembly for use in coating elongated metallic conductors and the like with liquid coating material, said assembly comprising a die consistlng of a flat plate provided with an aperture slightly larger in diameter than the elongated article to be received therein, a plurality of transverse rods slidably supporting said die for limited transverse movement thereon, and a stop spaced from said die for limiting the longitudinal movement thereof.

EDWARD J. FLYNN. 

